The functioning of the Open Shortest Path First (OSPF) protocol is dependent on the underlying topology. Based on the topology, networks can be broadly classified as broadcast multi-access networks, non-broadcast multi-access networks and point-to-point networks.
OSPF network Point-to-Point is default option for point-to-point interfaces such as HDLC, PPP or point-to-point NBMA subinterface. It uses multicast hellos OSPF messages and sent it on multicast address 220.127.116.11 and there is no Designated Router (DR) and Backup DR (BDR) election.
No special design consideration needs to be taken into account for point-to-point OSPF interface. Configure OSPF on a point-to-point link by enabling an OSPF routing process and specifying the interface on which OSPF should be run.
Perform these steps:
Configure an OSPF routing process by issuing the "router ospf" command in global configuration mode.
Define the interfaces on which OSPF runs and define the area ID for those interfaces by issuing the "network area" command in router configuration mode.
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#router ospf 100
R1(config-router)#network 10.0.0.0 0.255.255.255 area 0
To verify the network type use "show ip ospf interface" command
R1#show ip ospf interface s0/0
Serial0/0 is up, line protocol is up
Internet Address 10.1.1.1/8, Area 0
Process ID 100, Router ID 10.1.1.1, Network Type POINT_TO_POINT, Cost: 64